I'm signed up to do a beginner agility class with one of my dogs, and on the equipment list is a "short tab lead." Dog and I are both new to this, and thus I'm not familiar with some of the equipment.
I've Googled "short tab lead" and gotten everything from little 4-inch straps with a clip to 5-inch loops with a clip to leash handles with a clip to what I've thought of as traffic leads (~12 inches with loop included in length).
What should I be getting and in what material? Preferred retailers?
You shouldn't have to special order anything - if you've got an old, fairly thin (1/2" or smaller) leash lying around, just cut it off and knot the end. (Or you can easily make one with a small bolt snap and a bit of extra leather or nylon cord.)
Just make it long enough that you can grab it, and don't leave a loop and you should be fine.
make sure it doesn't have anything that could get caught on the equipment- no loops, knots, or braids. Easiest is to cut down an old lightweight lead as someone else suggested- if you don't have one, go buy a cheap cat's leash and chop it off- you want something that you can grab if necessary but not long enough such that dog might trip over it.
Cutting down a cheap leash is a good suggestion if you are on a budget, but there are some advantages to a leather "pull tab". My store doesn't sell these, but I bought one from Leerburg a few years ago, and it is extremely well made. I just checked the Leerburg site, and they are still only cost $10.00. The advantages of a pull tab are that they have a second ring at the end. This way you can attach your regular leash to the pull tab. When you are releasing your dog or collecting your dog back up again, you just attach your regular leash to the pull tag. I use the pull tab a lot, even outside of the agility ring.
The link above is a picture of my female Boerboel on the table during agility training as she wears the pull tab I purchased from Leerburg. Someone took this photo of me and the dog -- she is focused on me. Good girl!
I'm not affiliated with Leerburg -- it's just where I bought it. I think there are other places where you can buy them.